Politics has always thrived on blurred lines between candidates and interest groups, campaign backers, rich activists, and community leaders. In the wake of the Supreme Court's Citizens United decision, however, outside groups (spectators in the arena, if you will) have played an increasingly large monetary role in elections large and small, most famously in the presidential election, but extending deep into local elections. This holds even more true when it comes to high-influence, high-population cities like New York City, which this year is electing a vast slate of new candidates including mayor. This election has seen an enormous outpouring of outside spending on the NYC mayoral race, especially when it comes to the Democratic primary. Here are a few of these major outside groups, whose spending, spread out over months, has certainly affected the ebb and flow of the mayoral race.

1. United Federation Of Teachers

When we think "outside spending," it's usually corporations who come to mind, but with the education system becoming further and further embroiled in controversy over efficiency and charter schools, it makes sense that this would be a key race for educators' unions such as UFT. The United Federation of Teachers, through its political spending body, "United for the Future," has spent the most money of any group in the race, contributing close to (or more than, according to some estimates) one million dollars to mayoral candidate Bill Thompson, who has pledged to adopt some key policies the UFT favors. This puts the UFT not only ahead of the pack in spending (to put it in perspective, they spent almost $621,000 in the last three weeks of August alone), but also pushes Thompson to the forefront of recipients from a single outside donor, a distinction that has not proved as effective as hoped after a recent Quinnipiac poll put him at a close third after front-runner Bill de Blasio and City Council Speaker Christine Quinn.

2. NYC is Not For Sale 2013

Proving that irony still exists in politics, NYC is Not For Sale 2013 has spent almost as much as the UFT on this mayoral race — but in a very different direction. It is not a single union or corporation, but rather a coalition of left-leaning donors who have as their common objective preventing former Speaker Christine Quinn from winning the race. They have put nearly one million dollars to this end, a huge amount for a series of negative, rather than positive, campaign advertising. The coalition ranges from disenchanted Quinn supporters, to animal-rights activists (Quinn supports keeping horse-drawn-carriages legal, while de Blasio does not), to supporters of the other Democratic candidates. This level of spending is even more ludicrous because of the lack of focus of the group outside of its opposition to Quinn, with many of the backers undecided in their support or leaning towards de Blasio, John Liu, or Bill Thompson.

3. Hotel Trades Council

Seen as one of the more politically influential unions in New York, the HTC has committed to spending over two million dollars in this race (although it is further down the list because, to date, it has spent only about $650,000), which has gone a long way toward helping its preferred candidate, Speaker Quinn. Quinn, who has captured endorsements by more major unions than any other candidate, was heavily against outside spending during the height of the anti-Quinn ads by NYC is Not For Sale 2013, but she took a less firm stance once the HTC fell in behind her, a move that has drawn marked criticism. The HTC, a hotel workers' union, had been one of the most sought after endorsements by Quinn, who had actually focused on them during a speech given earlier this year.

4. Correctional Officers' Union

Here's where the line starts to blur a little, as it often does in campaign finance. While the COU (or, rather COBA, the Correctional Officers' Benevolent Association, which plays the direct political role) has not technically liaised with a candidate, it has independently spent more than $200,000 on a popular radio spot in support of John Liu, the mayoral candidate denied public funds earlier this year for his "suspect" financial dealings. Many have questioned the arrangement, which featured a campaign-produced clip being converted to a radio spot. While the clip was produced by Liu and featured his own son, the conversion to radio was purportedly independent of the campaign, a move that has cast doubts on the exact legalities of campaign and independent expenditures. Coming in the wake of high-profile corruption arrests in Liu's campaign and his rejection for public financing, this sort of deal may do more harm than good — but that's a matter for the citizens of New York to decide.

5. New Yorkers For Proven Leadership

Although New York is a very left-leaning city, there is still a very significant Republican presence, which is why NYPL has put forward significant support for Republican candidate and former MTA chief Joseph Lhota, one of the leading GOP candidates for mayor. This includes multiple $100,000+ donations by the Koch Brothers, influential right-leaning activists who have often taken interest in municipal and national politics. As the major Republican donors in this race, they have had a proportionally large effect, with Lhota receiving a large boost from their money.